Primarily in business applications, multi-party communications or conference calls among spatially dislocated parties are widely and frequently used to communicate effectively. For conferencing within a single communication system, a single connection topology, typically, the fully inter-connected mesh or star, is generally selected. This single connection topology assumes that all bandwidth is created equal, whether the bandwidth crosses a Local Area Network or Wide Area Network. For conferencing between/among peer-to-peer systems, where each system produces its own local conference, dumbbell topologies are typically selected.
The fully inter-connected mesh, an example of which is shown in FIG. 1, requires significant bandwidth and conferencing resources since each conference participant needs to construct their own composite sum of the other parties, and each conference participant needs to transmit their signal to all other participants. Referring to FIG. 1, first, second, and third port networks 100a-c are controlled by a common enterprise switch 104. The port networks 100a-c are located at different geographic locations 108a-c. At each location, a party (not shown) uses a corresponding communication device 112a-c to conduct a conference call with the other parties. The communication device of each party transmits a unidirectional audio stream 116a (for device 112a), 116b (for device 112b), and 116c (for device 112c) to the other communication devices. This configuration is acceptable when the connection network is proprietary. In a full mesh N party conference, the required numbers of transmitted streams is (N(N−1)) and of conference points is N. A 3-party conference call, such as shown in FIG. 1, would produce six unidirectional audio streams to cross the intervening Wide Area Network or WAN and require three conferencing points. As will be appreciated, full mesh is commonly used for a center-stage switch or asynchronous transfer mode connected port networks and not for IP WAN networks.
To reduce the required bandwidth resources, a star topology has been used, where each party sends its signal to a central conferencing or master circuit (where conferencing occurs), which is typically in a gateway. Referring to FIG. 2, the hardware configuration of FIG. 1 is depicted. Unidirectional audio streams 200a-c (among the devices 112a-c) are transmitted between the parties. The third port network 100c is the master and provides the conferencing circuit, while the first and third port networks 100a,b are the slaves and receive the audio streams provided by the master. The first port network 100a transmits audio stream 200a (which is the audio stream received from the first communication device 112a) to the third port network 100c and receives, from the third port network 100c, audio streams 200b,c (which, respectively are the audio streams received by the second port network 100b from the communication device 112b and by the third port network 100c from the communications device 112c). The second port network 100b transmits audio stream 200b to the third port network 100c and receives, from the third port network 100c, audio streams 200a,c. In a star topology N party conference, the required numbers of transmitted streams is 2N, and of conference circuits is one. For example, in FIG. 2 the three-party conference call produces six unidirectional audio streams to be transmitted over the intervening WAN and require one conferencing point.
A compromise between the fully inter-connected mesh and the star is a dumbbell topology, where each participant sends its signal to a local conferencing point, the signals are partially summed or combined, and the partial conference sum is then sent to other local conferencing points. An example of a dumbbell is shown in FIG. 3. A first gateway 300a controlled by a first server (not shown) in a first enterprise 304a is in communication via a WAN (not shown) with a second gateway 300b controlled by a second server (not shown) in a second enterprise 304b. First and second parties using first and second communication devices 312a and b are in a conference call with a third party using a third communication device 312c. The audio streams of the first and second parties are combined or summed to form a combined audio stream 316a and transmitted to the second gateway 300b. The second gateway meanwhile transmits to the first gateway the audio stream 316b of the third party. In a dumbbell topology N party conference call with M locations, the required numbers of transmitted streams is 2N+2(M−1) and of conference circuits is M. For example, in FIG. 3, the three-party conference call produces two unidirectional audio streams to be transmitted over the intervening WAN.
Apart from bandwidth requirements, the star and fully inter-connected mesh generally allow each party full flexibility in determining the set of other parties that they may be connected to. For example, in the examples of FIGS. 1 and 2 the second party can choose to speak and/or listen only to the first party. This selective listening is known as a sidebar. The dumbbell topology commonly does not allow a receiver to connect to a subset of parties from a remote location since they only receive a combined conferenced sum of the entire remote location.
There is a need for a conferencing system that can balance bandwidth requirements against the need to provide the conference participants with various conferencing features, such as selective listening.